INTRODUCTION 

In the realm of digital fabrication and design, the need for tangible, three-dimensional prototypes is essential to the iterative process. However, while modern society strives to reduce reliance on single-use plastics, known for their carbon emissions and large-scale pollution, their convenience and durability remain difficult to replace. Fortunately, extensive research has led to the development of bioplastics, now widely applied in industries such as pharmaceuticals, packaging, architecture, and digital fabrication. Unlike conventional plastics, bioplastics are derived from renewable resources and decompose naturally, minimizing pollution and reducing dependence on fossil fuels. As these materials break down, they leave behind little to no carbon footprint, offering a sustainable alternative without disrupting the workflow of digital fabrication.

WHAT IS POLYLACTIC ACID?

Bioplastics are all derived from natural materials, but polylactic acid is the one most commonly used for representational design. It is a thermoplastic derived from the lactic acid of corn, sugarcane, or biomasses with similar molecular structures. A thermoplastic is any plastic that becomes moldable under heat. Due to its compatible chemical properties and affordable price, PLA is widely used as filament for 3D printing and is the only commercially available bioplastic that is biodegradable and biobased. 

APPLICATIONS

Due to its versatile qualities, there’s a few applications for PLA, such as packaging, medical implants, textile fibers, and 3D printing. The chemical properties of PLA makes for a strong yet lightweight filament with a low melting point, enabling 3D printing to be accessible in both studios and at home. However, there are some differences that do set it apart from its petrol based counterpart. Due to the biodegradable nature, it is a more brittle material. 3D prints can have a visibly poor quality if the PLA filament is not stored in a cool, dry environment, as it is prone to moisture absorption. Despite these drawbacks, PLA has proven to be a useful material in the digital fabrication world for not only smaller designs, but can be applied to larger scale projects that do need structural integrity and longevity.  

PHANTOM FABRICATION

In medical practice, commercially available Rando phantoms are often used in radiation therapy for dosimetry and to evaluate how much radiation is optimal for treatment. However, these accurate models can be expensive. To develop an equally customizable but more accessible alternative, researchers have explored the use of 3D printing technologies. In a notable study, a team fabricated a heterogeneous head phantom by combining plaster powder and PLA powder in an attempt to replicate the properties of the commercial Rando phantom. 

Workflow for preparing a phantom composed of plaster mixed with PLA powder. Source: The Phantom Laboratory, Salem, NY, USA).

The process began with acquiring a patient’s CT scan using a Philips Big Bore Brilliance CT scanner. The imaging data was then imported into Mimics 21 software to model the air cavities, bone structures, and soft tissues. Subsequently, the model was sliced using CURA software and printed with PLA filament on an Ultimaker S5 3D printer. To accurately represent bone tissue within the head, the researchers experimented with different ratios of plaster and PLA powder, which were poured into the air cavities of the printed model.

(a) Commercial Rando head phantom, (b) Rando head phantom printed using only PLA material, (c) Rando head phantom printed with a mixture of plaster and PLA powder.

This study exemplifies the integration of digital fabrication software and bioplastics in the medical field, highlighting the potential of 3D printing to not only reduce costs but also allow for greater customization in prototyping as a whole.

INJECTION MOLDING

Injection molding, while not as widely accessible as 3D printing, remains the most common method for producing polymer parts and plastic products. A study using PLA as the injected polymer demonstrated that this material could make the process both more accessible and sustainable. Since PLA is already a popular choice in prototyping labs as an affordable and convenient filament for FDM printers, it makes sense to expand its use to other fabrication methods. Its lower melting point and reduced harmful emissions further support its suitability for injection molding.

Mold Inserts and Injection-Molded Parts. Source: Photo by Muenchinger; Parts Designed by Robert Austin and San Goovaerts 2020

Rhinoceros CAD Model. Source: Robert Austin and San Goovaerts 2020

However, the use of PLA pellets in this process is still in early development. Challenges such as trapped gas and difficulties in removing the plastic from the mold present obstacles in this method. Additionally, PLA pellets are less accessible compared to filament. Despite these limitations, ongoing research and material advancements continue to refine its potential for wider adoption in prototyping and manufacturing.

FUTURE OF PLA

As bioplastics research advances, polylactic acid has yet to replace its petroleum based alternative fully. However, the increasing integration of PLA in digital fabrication reflects the commitment of material researchers to developing more accessible and sustainable alternatives for prototyping and representational modeling. While not yet fully optimized, recent studies and experiments demonstrate significant progress toward a more sustainable approach.

REFERENCES

SyBridge Technologies. “What Are PLA Bioplastics?” SyBridge Technologies, 22 Nov. 2023, sybridge.com/pla-bioplastics/#:~:text=PLA%20bioplastics%20are%20made%20from,seaweed%2C%20or%20even%20shrimp%20shells

Gianeco. “What are the applications of PLA?” https://www.gianeco.com/en/faq-detail/1/5/what-are-the-applications-of-pla

Tasos Polygenis “What is PLA Filament? Composition, Advantages, Applications” Wevolver, 8 Aug, 2024. https://www.wevolver.com/article/what-is-pla-filament-composition-advantages-applications

S.Y. Kim, J.W. Park, J. Park, et al., “Fabrication of 3D Printed Head Phantom Using Plaster Mixed with Polylactic Acid Powder for Patient-Specific QA in Intensity-Modulated Radiotherapy,” Scientific Reports 12 (2022): 17500, https://doi.org/10.1038/s41598-022-22520-6.

Muenchinger, Kiersten, and Mike Bartell. 2023. “Desktop Injection Molding with PLA in the Academy: Increasing Manufacturing-Based Experiential Learning.” International Journal of Design Education 17 (2): 197–211. doi:10.18848/2325-128X/CGP/v17i02/197-211